Weight distributing trailer hitches are well known in the art to distribute the weight of the trailer relative to the tow vehicle. Such weight distributing hitches typically employ a cantilevered spring bar mounted in a ball mount hitch head attached to a towing vehicle. Flexing of the spring bar is accomplished by elevating its distal end upwardly toward the trailer tongue via a lift bracket mounted on the side of the trailer tongue. Typically, the lift bracket hooks a selected link of chain attached at the rearward end of the spring bar so operation of the lift unit pulls upward on the rearward end of the spring bar flexing the spring bar to a desired degree of flex.
A representative example of an improved weight distributing hitch assembly is shown and described in copending U.S. patent application Ser. No. 60/029,361 filed Oct. 28, 1996 entitled Weight Distributing Hitch Assembly, and design application Ser. No. 29/061,687 Oct. 28, 1996 entitled Ball Mount Head for a Weight Distributing Hitch.
A representative example of an improved lift unit for a weight distributing trailer hitch is disclosed in U.S. Pat. No. 4,815,752. A lift unit which embodies the invention disclosed in this patent and has achieved great commercial success is sold by Draw-Tite, Inc. under the trademark LIFT-LOCK.RTM. and part No. 3227. This lift unit includes a bracket member that is securely fastened to the frame of the trailer tongue, and a hinge member pivotally joined to the bracket member. A chain engaging hook is welded to the hinge member. A handle engaging hook is welded onto the hinge member above the chain engaging hook. The handle engaging member receives a handle tool to aid in rotating the hinge bracket to raise and lower it to flex and unflex the spring bar. A gravity responsive locking pawl is pivotally connected to the hinge member so that the bottom edge of the pawl rests in a notch on a top edge of the bracket member to restrain the hinge member once the spring bar has been flexed upon sufficient upward rotation of the hinge member via the handle tool which engages the handle hook. A cotter pin is manually inserted through aligned apertures in the pawl and the hinge member to lock the pawl in the notch engaging position.
The handle tool must be manually held in engagement with the handle engaging member and against the tension of the flexed spring bar with one hand while the other hand manipulates the cotter pin into the aligned apertures to lock the pawl in the latched position. Furthermore, when the hinge member is rotated to the lower position the user must manually remove the cotter pin and unlatch the pawl with one hand while the other hand holds the tool against the tension of the chain by the flexed spring bar.